I bought a Heat Pump

michaels

Reed_Richards said:

michaels said:

I was also surprised to hear that weather comp wasn't mentioned, we have this with our 10 year old gas boiler which along with a wide modulation range means it can run almost 24/7 in most circumstances, 

My gas boiler from 1998 monitored the outside temperature and the room temperature and knowing the required room temperature decided how much to modulate its output.  I was very disappointed that the Heat Pump did not seem to be as smart and seemingly cannot modulate down to a very low power.  The consequence is that it cycles, relying on a buffer tank to keep the interior water temperature more constant. 

michaels said:

When I was investigating options, bore hle GSHP seemed least likely to suffer from COP falls over the season (assuming you avoid freezing the subsoil which immediately reduces heat transfer).

Swings and roundabout here.  If the air temperature is lower than the underground temperature then the GSHP beats the ASHP.  But if the air temperature is higher than the underground temperature then the ASHP beats the GSHP.  You really need both and a system that chooses which to use depending on the outside air temperature.  Now that really would be weather compensation!  

Agree to an extent, except the periods when you need most heat output will also be when the air is coldest and given the way heat pump efficiency with respect to temperature I guessed that the ground source would achieve a higher scop - it was just a guess though, for us our high year round hot water requirement might I guess impact the other way.

Reed_Richards

shinytop said:

I made some enquiries about the quote I got and was told the rad temperature varied between 45-55 depending on outside temperature, based on an inside temp of 21.  I assume this is the weather compensation mentioned?  He also said all this is adjustable but that's what's used to size the system along with the EPC. 

You need to pin this down because the temperature setting affects your RHI payments.  Top line of my MCS certificate states the flow temperature (50 C) and the SCOP (3.2).  If the flow temperature were set higher then the SCOP would be lower and that would reduce the RHI payments.  But the lower the flow temperature, the larger your radiators need to be.  Starting from scratch, I would be tempted to think about how large I could tolerate the radiators to be and use that to determine the maximum flow temperature.  

matelodave

For those who feel the need, here is some info on what SCOP is and why its different to COP https://www.bregroup.com/heatpumpefficiency/background

shinytop

Reed_Richards said:

shinytop said:

I made some enquiries about the quote I got and was told the rad temperature varied between 45-55 depending on outside temperature, based on an inside temp of 21.  I assume this is the weather compensation mentioned?  He also said all this is adjustable but that's what's used to size the system along with the EPC. 

You need to pin this down because the temperature setting affects your RHI payments.  Top line of my MCS certificate states the flow temperature (50 C) and the SCOP (3.2).  If the flow temperature were set higher then the SCOP would be lower and that would reduce the RHI payments.  But the lower the flow temperature, the larger your radiators need to be.  Starting from scratch, I would be tempted to think about how large I could tolerate the radiators to be and use that to determine the maximum flow temperature.  

Yup I know and the the quote I have states a SCOP of 3.2 so I am hoping that's what will end up on my MCS certificate.  I've decided to go with this quote after having had a couple of similar ones.  I liked the guy who came and they are local.  I have been thinking the same about the radiators and would rather go up a size to be on the safe side.  

Reed_Richards

shinytop said:

Yup I know and the the quote I have states a SCOP of 3.2 so I am hoping that's what will end up on my MCS certificate.  I've decided to go with this quote after having had a couple of similar ones.  I liked the guy who came and they are local.  I have been thinking the same about the radiators and would rather go up a size to be on the safe side.  

Upsizing your radiators will add to the cost but very little as a percentage of your £16k total.  So before you start, ask your chosen installer if they can offer you an alternative quote for bigger radiators and a higher SCOP.  

Cardew

 A new firm 'Cardew Installations ltd'! will give you a competitive quote with a SCOP of 4.0!

If after 12 months your subjective opinion is that the SCOP is way below 3.0; how do you confirm that opinion and what action do you take?

  Cardew installations ltd will have ceased trading of course.

shinytop

Cardew said:

 A new firm 'Cardew Installations ltd'! will give you a competitive quote with a SCOP of 4.0!

If after 12 months your subjective opinion is that the SCOP is way below 3.0; how do you confirm that opinion and what action do you take?

  Cardew installations ltd will have ceased trading of course.

Don't I want to keep quiet because if it came out that you fiddled the SCOP I might get my RHI reduced?  

Reed_Richards

Cardew Installations Ltd needs to be an MCS certified installer or you won't get the RHI at all!

Cardew

Reed_Richards said:

Cardew Installations Ltd needs to be an MCS certified installer or you won't get the RHI at all!

Getting one person certified isn't that difficult - there are websites that guarantee they will get you through certification; MCS only check your initial installation.  Once one person in the firm is certified you can get any employee to carry out the work, and you self-certify any future installations.

We have all seen the cowboy firms operating virtually unchecked in the solar industry when you required MCS registration to get Feed in Tariffs; and why should it be any different with heat pumps when the post gas CH boom takes off?

The original EST trial of heat pumps showed many installations had a system COP of well below 2.0; iirc one was 1.2 and several at 1.6.

The contributors on this forum know the pitfalls and are here to give or receive advice; not so Mr & Mrs Average. Read the brochures that the said Mr and Mrs Average will peruse. Like this from a major manufacturer:

'They operate efficiently even in cold temperatures. Just 25% of the energy used by a heat pump is provided by electricity, with the remaining 75% being generated by the environment through the ground, water or air'

That means a system COP of 4.0 for an ASHP even in cold weather, doesn't it??? With enough piping hot water for hot baths for the whole family.

Get a quote from Cardew Installations Ltd and the salesperson will have that quote to hand.

matelodave

I'd expect Cardew Installations Ltd to be an honest ethical company and tell the truth.

However, as the real world COP of heatpumps is much like real world MPG for a car I'd guess that unless you get customers who have a pretty good idea of what they are signing up for, I doubt that CIL would last everso long.